well after killing 1 x a12, 1 x a14 and 2 x a15

its time i built a motor to handle this buisness (it's kinda funny, normally people do up there motor and blow every other bit of drivetrain, i've done the opposite)

the a12 had a blown head gasket when i got it

the a14 blew the rings

and both the a15's stuffed the rings, i'd like to re-build one of the a15s (one has stock cam and lightened crank, the other just a mild NA street cam)

plan:

1 bar (14-15psi) boost all day every day

questions:

- i'd love to get an a-14 pulsar low comp head if anyone has one? (this will be my way to lower compression)

- what should i do with the head gasket? what material etc etc? i dont want to o-ring though.

- and most importantly as they seem to be the weakest point... rings... what do you do to make them robust for boost?

- and lastly what would be any other weaknesses to engineer out? im sure it can be done with stock pistons and stuff, i dont think i need to get that serious???

14-15psi all day on Aseries is alot.. You would have to put some decent gear in one to keep it reliable and handle a good boot here and there. Stock CA's are good for 14-15psi everday and have a few more goodies than Aseries. I think a decent set of Chromie's and rings would be a good investment.

About time you started getting back on here rallycar ...Keep up the Aseries power

im building a CA aswell, but lets keep thread about a-series

Lock the timing. Be it Dizzy or computer controlled.

To lower compression, you can open up the combustion chamber. Simple, cheap and easy.

Ridgecrest will do a copper head gasket up to 3mm if you want to do that as well.

I would look at a reduced boost setting.

Open your ears to detonation. . . If it detonates, back off and dig further. . .

Once everything is running sweet, start winding the boost and timing in. You should be able to here a change in the "song" of the engine before detonation hits. This is when you wind a bit of boost/timing out.

Better off a few HP down then a few engines down. . .

Are you a M.E.????

How about using rings designed for a turbo car???

Its not how much boost you run that matters, its about controlling detonation. Something you don't seem to know how to do!!!

A low static comp, intercooled motor should??? have no probs?? Why not do it properly this time and run a 3D computer???

what has Mech Eng got to do with building a turbo a-series?

how bout answering my question about rings on which ones to get and where from?

controlling boost has been the problem, that and injectors maxing out

how am i not doing it properly with the computer i have?

it seems you have a VAST knowledge, so feel free to actually answer my questions instead of trying to make me feel stupid, and i am un aware of the effects of detonation on rings so if there is some link between the two please enlighten me on that too

thanks for any help,
Michael

all those ring failures do suggest you are having problems with detonation. cast rings are brittle and the shock waves caused by detonation will crack them. then they will overlap eventually in the grove and crack the piston headland. trying to find rings that will survive the poor tune is only a band-aid measure, and the detonation will eventually damage some other component - like pistons or big ends.

Controlling detonation means controlling boost (within the efficiency of the turbo), mixtures, timing, and temperature - both inlet air temp and coolant temps.

Also while the head is off, smooth all the sharp edges in the combustion chamber with an emery flapper wheel. a sharp edge (or particualrly a point like you find in most peanut chambered heads) can be a hot spot causing detonation.

ACL, Grant and the other aftermarket piston/ring manufacturers do not list moly rings. Their "Chrome" rings are chrome plated black (cast) rings. these will be no more durable than normal black rings.

Chromemoly rings might be available from Nissan, but the standard cast pistons are a weak point too. Really you should be getting forged pistons made up, and in that case I'd go and research suitable moly rings and have the piston made to accept them. A slightly cheaper alternative may be to search the Wiseco motorbike piston catalog for a suitable piston WRT pin, bore, deck height, and head profile. Alot of these are forged and come with moly rings.

Aiming for a certain target boost pressure isn't the way to go. 14psi doesn't mean it will make more power than 10 or 12psi for example. A well designed setup (manifolds, suitable cam, good flowing head) will make more power at lower boost than a setup with inherent design problems, and simply trying to overcome it with more boost. It's highly likely that the very small turbos you are using are producing more heat than anything else at those boost levels.

thanks for the info, the reason i want the motor to handle the 14psi is that i struggle to throttle the turbos back from that sort of level

i've always had the problem of injectors maxing out, i suppose this is terrible for mixtures and probably the cause of detonation?

the tune up has never been that great which i put back to the choice of workshop to tune it, but i never wanted to spend the right money to tune it properly until i fixed up the injectors and other problems

I have to agree with L18_B110, eveything he said is pretty much on the money.

I took timing out of my suck through stromberg fed A12 turbo, it made less boost and 27kw atw more...

I was concerned with it blowing up, but as the tuners say, if the tune is right (mixture, timing, and boost control) you shouldnt have a problem...

It does sound like the tune is the issue, maxed out injectors is a HUGE NO NO!! If the fuel pump starts to struggle or loose pressure then it will lean out for sure...

First item of business, sort them injectors out.

Until this is done I wouldn't start on the engine. . .